Conventional drop-on-demand inkjet printers are commonly categorized based on one of two mechanisms of drop formation. A thermal bubble inkjet printer uses a heating element actuator in an ink-filled chamber to vaporize ink and create a bubble which forces an ink drop out of a nozzle. A piezoelectric inkjet printer uses a piezoelectric material actuator on a wall of an ink-filled chamber to generate a pressure pulse which forces a drop of ink out of the nozzle. Piezoelectric printheads may have several advantages over thermal printheads including that, for example, they jet a wide range of ink formulations, they do not raise the temperature of the ink significantly which can cause drying of the ink in the nozzle, they have a longer working life, and the deformation of the piezoelectric ceramic material responds proportionally to voltage changes unlike bubble generators and therefore may produce multiple drop sizes, as well as limit the formation of unwanted satellite drops, which enables more control over the quality of the printed document.
A convenient way of constructing an array of piezoelectric actuators for an inkjet printhead is to bond a single piezoceramic plate (or sheet) onto a diaphragm plate (or sheet) covering a corresponding array of pressure chambers. The piezoceramic plate has a single common electrode on one side and a number of individual electrodes on the other side, each individual electrode corresponding with the location and shape of an associated pressure chamber. For each individual electrode on the piezoceramic plate, there is a matching conductor on the diaphragm over the associated chamber. Subsequent to bonding the piezoceramic plate to the diaphragm, portions of the piezoceramic plate including electrodes on one or both surfaces not over the conductor may be removed. The problem with this way of constructing the array of piezoelectric actuators over the pressure chambers relates to the accuracy with which the individual electrodes on the piezoceramic plate can be located with respect to the diaphragm conductors and pressure chambers when the piezoceramic plate is bonded to the diaphragm. That is, if the piezoceramic plate is not located over the diaphragm in a precise manner, the individual electrodes on the piezoceramic plate will not be properly aligned with their respective diaphragm conductors and pressure chambers. As a result, a portion of the piezoceramic plate not centered over the pressure chamber will be actuated. Thus, deviations in the alignment result in less output from the actuator, pressure pulses that are not spatially symmetric, and possible short circuiting of electrodes between neighboring chambers.